Photonic switching in high performance datacenters [Invited]

Abstract

Photonic switches are increasingly considered for insertion in high performance datacenter architectures to meet the growing performance demands of interconnection networks. We provide an overview of photonic switching technologies and develop an evaluation methodology for assessing their potential impact on datacenter performance. We begin with a review of three categories of optical switches, namely, free-space switches, III-V integrated switches and silicon integrated switches. The state-of-the-art of MEMS, LCOS, SOA, MZI and MRR switching technologies are covered, together with insights on their performance limitations and scalability considerations. The performance metrics that are required for optical switches to truly emerge in datacenters are discussed and summarized, with special focus on the switching time, cost, power consumption, scalability and optical power penalty. Furthermore, the Pareto front of the switch metric space is analyzed. Finally, we propose a hybrid integrated switch fabric design using the III-V/Si wafer bonding technique and investigate its potential impact on realizing reduced cost and power penalty.

Exploration of VCSEL ultra-low biasing scheme for pulse generation

“…For DFB-based edge emitters, which require a much larger footprint than a VCSEL, the current record for power consumption is just under 100pJ/bit [30]. Since current VCSEL cavity designs are capable of transmitting at 35Gb/s with an energy cost of 145f J/bit [31], it is reasonable to expect, by extrapolation, that applying a modulation in the nonlinear response region should provide transmission rates exceeding 10Gb/s with an energy cost of the order of 50f J/bit, thus potentially enabling the technology to approach the needs of datacenters [32].…”

Photoconductive heaters enable control of large-scale silicon photonic ring resonator circuits

“…The miniature size of silicon ring resonators make them attractive candidates for large-scale photonic systems as they can be densely integrated on-chip for lowering size, power-consumption, and cost [1][2][3]. As a result, numerous solutions based on ring resonators have been proposed for applications in communications systems [2,[4][5][6], signal processing [1,7], quantum computing [8], sensing [9], and machine learning [10]. A key requirement for the practical use of these systems is the ability to precisely control the resonance conditions of their ring resonators, which allows to 1) correct for fabrication errors, 2) adapt the system in real-time to account for temperature variations or laser wavelength fluctuations, and 3) reprogram the system altogether for implementing various transfer functions and different functionalities.…”

Open loop control theory algorithms for high-speed 3D MEMS optical switches

“…As the world attempts to reduce its carbon footprint and use electrical power more efficiently, the size and number of data centers continues to grow exponentially [3]. In response to this threat, there is a world-wide effort to develop all-optical technologies to replace electronic transmission and switching/routing, two major consumers of power in modern data centers [4,5].…”